Possible Nutritional Deficiencies of the Vegetarian Diet

Possible Nutritional Deficiencies of the Vegetarian Diet


La Vegetarian diet it is a nutritional regime based on the prevalent or exclusive consumption of foods belonging to the plant kingdom.

Today, vegetarian diets are considered more than anything else as a "set" of eating styles.

In this article, however, we will talk only and exclusively about the possible shortcomings related to some specific forms of vegetarianism:

  • Diet latto-ovo vegetarian (or only ovo-, or only lacto-): excludes meat and fish products, but includes milk and derivatives, and / or eggs;
  • Diet vegan: excludes any food of animal origin, therefore also milk and derivatives, eggs, honey etc. It can include microorganisms such as fungi and bacteria.

What possible deficiencies can manifest themselves in vegetarian diets?

Below we will only talk about "possible"deficiencies, as there are various discretionary factors that can make a difference on the nutritional balance of a vegetarian diet; for example: care in the choice of food sources, level of physical activity, any special physiological conditions (pregnancy, breastfeeding) or pathological conditions , use or not of supplements, stage of life (growth, old age) etc.

It is therefore first of all necessary to understand what are the nutritional functions attributable to the various food groups.

For further information: Vegetarian Diet: What It Is And How It Works

Missing Nutritional Functions

XNUMXst fundamental group of foods: meat, fish products and eggs

Includes fresh meat (rabbit, avian, beef, horse, pork, sheep, game, etc.) offal, fresh and salt water fish, other fishery products (crustaceans and molluscs) and all eggs.

Above all they bring protein ad high biological value (VB), iron highly bioavailable (heme and bivalent or Fe2 +), numerous Vitamins water-soluble products of the group B (thiamine or vitamin B1, riboflavin or vitamin B2, niacin or vitamin PP and cobalamin or vitamin B12).

How not to mention the other 3 great nutritional qualities of sea fishing products, namely the abundance of:

  • vitamin D3 (calciferolo: 1,25-(OH)2-colecalciferolo);
  • iodine;
  • fatty acids essential (EFA) of the biologically active omega 3 group, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

The other food rich in calciferol and polyunsaturated fatty acids, part of which is essential, is egg yolk.

Offal, such as the liver, kidneys, heart and spleen, are real reservoirs of valuable minerals and vitamins.

Warning! On the flip side, some of these products also provide significant amounts of cholesterol and saturated fats, which if introduced in excess are anything but healthy (especially in the presence of metabolic diseases). The abuse of processed meats - because they contain nitrates and nitrites - and of all other cooked meats by overcoming the thermal stability of fats and proteins, is correlated with an increased risk of carcinogenesis of the stomach and intestines.

In this sense, vegetarian diets play a protective role.

II ° fundamental group of foods: milk and derivatives

It includes all types of milk - even condensed and powdered milk - and all processing derivatives.

They too provide high VB proteins but, unlike the previous one, they contain less iron but a lot football bioavailable e phosphorus.

Warning! Again for "par condicio", we must report that also milk derivatives not skimmed they bring significant amounts of cholesterol and saturated fats.

Lack of Vitamins and Minerals in the Vegetarian Diet: How to Avoid It?

Speaking of important vitamins and minerals, because they are deficient in foods of plant origin or not highly bioavailable, the importance of including at least one of the 5 types of foods belonging to the first two basic food groups in the diet should be emphasized.

In fact, it is not vital, even if it is recommended, that they are all present in adequate quantities (neither excessive nor irrelevant). For this reason, a lacto-ovo-vegetarian diet, or only lacto-, or only ovo-, has a good chance of being balanced anyway; the same cannot be said for the vegan diet.

For further information: Supplements for Vegetarians

Excess of Vegetables

Excess of vegetables and anti-nutritional effect

Let's now move on to another drawback of vegetarian diets, namely the excessive presence of "potentially" factors negative from a nutritional point of view.

We know that these nutritional styles try to compensate for the deficiencies of vitamins, minerals and AGE more abundant in animal foods by over portioning some foods of the III, IV, VI and VII fundamental groups.

But what are these factors anti-nutritional? Among the main ones we mention sequestrators or chelators and enzymatic inactivators: phytic acid, oxalic acid, trypsin inhibitors, dietary fibers and lecithins.

Phytic acid and phytates

The acid phytic is a six-fold repeated dihydrogen phosphate ester of inositol (of the myo isomer), also called inositol hexakisphosphate (IP6) or inositol polyphosphate.

In vegetables (especially in the seeds of legumes, cereals and others), it has the nutritional role of storing phosphorus.

At physiological pH, the phosphates are partially ionized, giving rise to the anion phytite.

However, having a strong binding affinity with other minerals in the diet, such as calcium, iron and zinc, they can bind and inhibit intestinal absorption.

Cooking has a harmful action on the molecule inactivating it. The soaking of dried legumes allows you to disperse a certain amount.

Oxalic acid and oxalates

The acid oxalic is an organic compound with the formula C2H2O4, diffused in the form of dihydrate (C2H2O4 · 2H2O.).

It has an acidic strength higher than acetic acid, constitutes a reducing agent and its conjugate base, known as oxalate (C2O2−4) represents a chelating agent for metal cations.

It is found naturally in many foods, but excessive dietary intake and even prolonged skin contact can be harmful.

It tends to bind mainly calcium and is abundant in the leaves of plants belonging to the Chenopodiaceae family (spinach, amaranth, etc.), Brassicaceae (cauliflower, broccoli, black cabbage, black cabbage, etc.), Polygonaceae (rhubarb, etc.), Arcaceae (Arisaema triphyllum ), Apiaceae (sorrel, parsley, etc.), Vitaceae (American vine, etc.), Oxalidaceae (carambola) etc.

It should be noted that, based on certain insights, citrus fruits produced in organic farming contain less oxalic acid than those produced in conventional agriculture.

The interest in this chelator also gravitates on the fact that the most common kidney stones are based on calcium oxalate; diet therapy consists of eliminating sources of oxalic acid, not calcium.

Again, cooking has a positive inhibiting effect.

Trypsin inhibitors

- inhibitors of trypsin (TI), belonging to the serine protease group (serpin), are peptides that reduce the biological activity of trypsin by controlling its activation and catalytic reactions.

Trypsin is an enzyme involved in the breakdown of many proteins, mainly involved in digestion human and other monogastric animals or young ruminants.

It is mainly contained in seeds such as legumes (especially soybeans) and cereals; its vegetal function is a deterrent towards animals and metabolic. It is also naturally present in the pancreas of some animals as a protective agent from the accidental activation of trypsinogen and / or chymotrypsinogen.

When taken with food, it acts as an irreversible and competitive substrate; in practice, it nullifies the proteolytic effect of trypsin.

Trypsin inhibitors also undergo heat degradation. Cooking eliminates its contents.

Dietary fiber

They are contained in all plants in their natural state.

Some dissolve in water, gel and slow down intestinal transit, others do not and are fermented by producing gas and stimulating peristaltic contractions.

Overall beneficial, because they increase satiety, modulating intestinal absorption, protect the intestine by lowering the risk of colon cancer, prevent constipation and related complications, nourish the intestinal bacterial flora, if in excess they hinder the uptake of useful molecules .

Too many fibers, in addition to being associated with higher levels of the other aforementioned antinutrients, can create both a hydrophilic and lipophilic mass (due to the presence of digestive fluids) capable of sequestering not only fats in general and cholesterol, but also essential lipids and fat-soluble vitamins ( vit. A, vit. D, vit. E, vit. K).


Lecithins is a controversial topic. Not everyone agrees on their potential anti-nutritional effect, or at least on the critical level.

Of great nutritional interest due to their ability to limit the intestinal absorption of cholesterol and to positively affect its metabolism, they can however have an inhibiting effect on the intestinal uptake of other lipophilic molecules such as vitamins and essential fatty acids.

Some seeds, such as soy seeds, are rich in lecithins, but also foods of animal origin such as egg yolk.

For further information: Sport and Vegetarian Diet: Benefits and Controversies

Who Risks the Most?

Who is at risk of nutritional deficiencies due to a vegetarian diet?

Not in order of importance, the following categories of the population are at greater risk of nutritional deficiency:

  • Who follows a vegan diet, or worse raw;
  • Those who follow a vegetarian diet and do not use food supplements;
  • Who is in the development phase, from the embryonic-fetal phase up to near adulthood;
  • Pregnant women and nursing women;
  • Senior citizens;
  • Those who, due to physiological conditions, have a greater nutritional need for some nutrients;
  • Who, due to pathological conditions, has a nutritional need for certain nutrients;
  • Athletes.

Let's now see the most frequent cases of possible nutritional deficiencies related to the vegetarian diet.

iron and anemia

Iron is an important mineral involved in several processes; the insufficiency in the diet is identifiable first of all by a reduced synthesis of hemoglobin of the red blood cells e anemia so-called sideropenica.

Highly bioavailable iron abounds in meat, fishery products and egg yolk. The intestine absorbs 20% of the ingested hemi iron and only 5% of the ferrous one.

Plant foods contain lower levels and usually very little bioavailable, both due to the chemical form, and due to any antinutrients.

Especially fertile and pregnant women have a greater need.


Vitamin B12 is cyanocobalamin

Vitamin B12 is involved in the synthesis of DNA, in the synthesis of red blood cells and regulates the metabolism of carbohydrates.

Although primarily bacterial, it is abundant in meat, fish and egg yolk. In plants it is almost absent and, in any case, not bioavailable.

The deficiency is very dangerous for the embryo-fetus, which risks irreversible malformations or abortion. It can also lead to pernicious anemia.

Vitamin D

It is a pseudo-hormonal factor that regulates the metabolism of calcium and therefore of the bone in the body; it is also involved in immune defense.

Those who often and frequently expose themselves to sunlight in the spring, summer and autumn period independently produce sufficient quantities by exploiting cholesterol as a precursor.

Everyone else must get adequate amounts in their diet, so they consume fish and egg yolk.

Significant deficiency impairs the achievement of peak bone mass and is a risk factor for osteoporosis - but not only.


We know that together with phosphorus it forms the basis of hydroxyapatite, a mineral of the skeleton, but it is also essential for various cellular processes.

It is very rich in milk and especially in seasoned derivatives, in a highly bioavailable form. In vegetables such as legumes it is present but lower and, moreover, conditioned in the absorption due to the presence of antinutrients.

A deficiency, rarer than that of vitamin D, can have an equal effect on the skeletal level (lack of or impaired growth and risk factor for osteoporosis).


Its presence in food is so scarce that even omnivores tend to be deficient.

It underlies the synthesis of thyroid hormones.

It abounds in foods of marine origin; seaweed, for vegetarians, is the only useful nutritional source.


They are the most biologically active omega 3s.

Semi-essential for all, children, the elderly, pregnant women and nurses have a greater need.

They have such a high number of functions that it is impossible to summarize in a few lines; we limit ourselves to saying that they play the role of precursors of anti-inflammatory eicosanoids, are essential for the development and maintenance of the nervous and ocular, and that they have a protective metabolic impact from atherosclerosis.

The primary source is undoubtedly that of wild fatty fish. Eggs also contain not negligible levels. For vegetarians, supplementing with oil from algae is a good solution.

Vitamin B2

Its deficiency is rare.

In the body, it forms the basis of the enzymatic cofactors FAD and FMN.

It abounds in milk and derivatives but modest quantities are also found in vegetables.

Essential Amino Acids

Even this possibility of deficiency is quite remote for most lacto-ovo-vegetarians.

It is different for the sports population who embrace the vegan philosophy. In this case, the high biological value protein mountain is almost always insufficient to support muscle protein turnover.

To remain compromised are therefore the post-exercise recovery and performance improvements, especially in strength activity. Food integration becomes essential.


Ultimately, the vegetarian diet can undoubtedly increase the risk of nutritional deficiencies, but the extent and type depend on numerous factors.

In addition to the nutritional correction by a dietician, food supplementation is undoubtedly the primary measure to avoid this hypothesis.

Let's not forget that sometimes the deficiencies remain in a sub-clinical condition even for a long time, predisposing to pathologies or complications in the long term even without any primary warning.

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